The diagnostic potential of the 14-3-3 family of proteins in the cerebrospinal fluid (CSF) of humans and animals infected naturally or experimentally with transmissible spongiform encephalopathies (TSEs) (Creutzfeldt-Jakob disease - CJD; bovine spongiform encephalopathy - BSE; and scrapie) was validated and improved. During the period of this report, more than 500 CSF and blood specimens were submitted to the LCNSS from more than 75 neurology services throughout the United States, the United Kingdom, Ireland, the European Community and the African continent. This study adds greater statistical significance to the sensitivity (98%) and specificity (97%) for the diagnosis of TSEs and supports a proposal for an amendment to the current internationally accepted clinical diagnostic criteria to include the 14-3-3 assay results in support of a clinical diagnosis of TSE.